Gas turbine engine parts are conventionally manufactured by an investment casting process. This process inherently has limits on how accurately dimensions, in particular small dimensions, can be made. Consequently, it is known to undertake additional machining operations on cast parts to, for example, refine dimensions, provide more intricate detail in features and improve surface finishing of the part.
FIG. 1 shows a prior known fixture. As can be seen the fixture comprises a baseplate 1 having an orthogonally extending side wall 5. Three clamps are arranged to hold a part on one of three orthogonal planes X, Y and Z. A first clamp 6 clamping in an X-plane, a series of two clamps 2 and 3 clamping in a Y plane and a third clamp 4 clamping in a Z plane. The Y and Z clamps are pivotal into and out of position by means of pivot 2a, 3a, 4a and can be latched into position by means of catches 2b, 3b, 4b extending from the side wall 5 and baseplate 1. The third clamp Z also includes a hinge 4b allowing an end of the clamp to be raised and lowered with respect to the base plate 1. The X clamp is a screw jack clamp with a swivel face end allowing engagement onto an uneven surface.
As can be seen, little of a clamped part is left accessible. Consequently a part may need to be repositioned in to fixtures multiple times for performing multiple machining/finishing operations. This is both time consuming and, since no one datum is fixed in position, the results after multiple operations are variable. Consequently, quality and conformity of parts to a desired specification may not be consistent. Accurate location of small parts is particularly challenging.
It is an object of the invention to provide a fixture which can hold a part securely during machining operations and which provides access to multiple surfaces reducing the need for repositioning the part between multiple machining operations.